With the generation born post-World War II now reaching retirement age and having substantially more disposable income than ever before, there has been an upsurge in interest in leisure activities. The business of providing vacations has developed into a major industry world wide. The spas and resorts have grown in popularity but can come at a substantial cost. The price one has to pay for a motel or hotel with meals and other necessities and/or luxuries has compelled the wise traveler to seek another less expensive mode of vacationing.
One can obtain the benefits of home comfort and conveniences using a campsite and the proper affordable means for camping. Whether the rationale is economy, communing with nature, or both, camping is an ideal way to vacation. However if one wishes to camp and have many of the benefits of home, one must go to a campsite and use the “hookups” provided by the commercial campsite owners, obviously for a fee.
The present invention relates to a camper which provides all of the convenience of home living and the benefits of traveling economically, while concurrently allowing the traveler to set up camp wherever he/she may desire.
There is another use for the trailer of the present invention which is diametrically opposite from that of recreational camping. The hostile environment in the world today and the natural disasters worldwide which seem to occur all too frequently today have resulted in a greater awareness to be prepared for any type of emergency that might arise, whether it be from natural disasters such as fires, earthquakes, flooding, etc., or from terrorists or saboteurs seeking to destroy the infrastructures of our cities or very specific targets.
When any catastrophic or emergency incident of the type mentioned above occurs requiring site management and/or rescue of personnel etc., it is imperative to promptly move men and materiel to the site of the disaster or scene of destruction so that rescue efforts can proceed promptly, smoothly and efficiently. The person in charge of the emergency operation must be able to communicate with his team members in the field so that all can be kept apprised of developments when they occur. In the past, the operation would be conducted using walkie-talkies or other rudimentary cellular devices or from a headquarters location far removed or remote from the scene of the disaster. This has not proven to be successful as the full array of support equipment is not on the scene to direct all aspects of the operation.
The solution to this problem found in the prior art is to use the trailer of the present invention in the form of an Incident Command Post (ICP) containing equipment and paraphernalia which can expedite a search/rescue operation. The incident command post trailer of the present invention, carrying within it all elements found in a command headquarters usually located at a site remote from the scene of activity in the past, is the answer to the stated problems found in the prior art.
U.S. Pat. No. 1,422,498 discloses a camping trailer which is designed to eliminate the discomforts and inconveniences noted by providing a trailer to be drawn by a car containing the campers, in which living necessities are either provided or ample space is provided for the packing and carrying of such articles that may be desired or necessary to take along.
U.S. Pat. Nos. 3,070,399 and 4,114,942 disclose expandable house trailers, each suitable for use as a camper. The trailers disclosed both possess bluff bodies facing the wind head on when being towed by a vehicle and therefore would generate substantial drag on the combination towing vehicle and trailer unit.
U.S. Pat. No. 3,070,399 discloses a truck mounted camper having a tent permanently mounted upon the top of the truck which can be unfolded to provide an additional enclosed area to the rear of the truck. There is no trailer in this disclosure and the tent in this case is stored on the top of the truck thereby increasing the drag the truck in normally subjected to.
U.S. Pat. No. 6,017,080 discloses a rectangular shaped tent camper with a slide-out room. When the camper is in its collapsed compact alignment with low profile, its front possesses a bluff body facing the oncoming air flow when moving forward and thus creates a substantial amount of drag.
Publication WO/1985/001260 entitled “Streamlining Device for a Towing Vehicle” relates to a trailer. Because of the design of trailers, they form a very high air resistance when trailed behind the moving vehicle. The reference discloses reduction of air resistance by covering the area between the roof of the trailing car and the front part of the trailer.
There is additional prior art in which the camping is done in a self propelled vehicle which is not relevant to the instant invention as the camper of the present invention is towed by a vehicle. The prior art disclosed above is irrelevant because they are “bluff bodies”, not streamlined, and as such, when in motion, the air flow will normally separate from all of the relatively sharp edges of the units disclosed thereby increasing the drag thereon.
With the price of gasoline and other petroleum based products rising exponentially, it is necessary to lower the costs associated with recreational camping if that sport is to continue to grow at a steady rate. The trailers found in the prior art consist mainly of “bluff bodies” which when moving behind a towing vehicle show a frontal area that is impacted directly by the air flow emanating from the rear of the towing vehicle which slows the towing vehicle to a considerable extent. The trailer of the present invention possesses a streamlined body facing into the oncoming wind stream behind the towing vehicle. The multi-purpose trailer is streamlined to reduce the resistance to forward movement resulting from the drag and yaw forces thereon and materially reduces drag.
The force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag (or air resistance). In characterizing drag, the term “parasite drag” is commonly used. Parasite drag is the sum of Pressure Drag (Form Drag) and Skin Friction (Viscous Drag).
The portion of the drag force that is due to the inertia of the fluid—the resistance to change that the fluid has to being pushed aside so that something else can occupy its space—is called the pressure drag (or form drag or profile drag).
Most parasite drag is caused by the pressure difference between the front and rear of the any other three dimensional “form” moving through the air. The amount of pressure drag depends upon the size and shape of the object.
Drag increases with the density of the fluid (ρ). An increase in the density of the fluid increases the mass of the fluid, which results in increased inertia, which in other words means more resistance of the fluid to getting out of the way of the vehicle seeking to occupy the location of the fluid and replace it. Drag also increases with area. (A), i.e., for purposes of this invention, area is the cross sectional area projected in the direction of motion. Taking the cross section of the object in the direction of its motion, this is the cylinder of fluid that must be cast aside to let the object proceed.
Fluids (air) also have viscosity. It is less apparent than with a liquid, however the air does cling to a body as it moves through it. This creates a small amount of skin friction on the surface of the body.
When any gas flows over a surface, the viscous effects are confined to a thin layer just above the surface of any object moving through a fluid. This is thin layer is known as the “Boundary Layer.” The boundary layer exerts a drag force on the surface over which it flows, trying to pull the surface along in the direction of the air. All viscous effects take place in the boundary layer. The average streamline velocity varies from zero at the surface to free stream velocity at the upper edge of the boundary layer. Free stream velocity is essentially synonymous with relative wind, which in turn equals the velocity of the vehicle. The amount of Viscous drag (skin friction) depends (inter alia) on three factors:                1. Velocity of the gas        2. Viscosity of the gas        3. Length of the surface over which the gas flows        
The inclusion of the “length” parameter means that more total drag will occur if fluid flows for many feet over a “long” object than if the same gas flows a short distance over a shorter object. Viscous Drag is the product of Velocity×Viscosity×Distance.
A streamline is a line along which a series of air particles move. Any particle on a streamline will follow the same path around an object as all the other particles on that streamline. Once a particle is on a given track it remains on that track (streamline) and follows the particle ahead of it.
Flow separation increases drag. When driving a vehicle which is pulling a trailer behind it, theoretically speaking, an area of low pressure will form over the windshield of the towing vehicle. An area of high velocity and low pressure will exist along the top of the vehicle. The airflow should decelerate as it turns downward along the back of the vehicle. This would cause the pressure to return to atmospheric pressure behind the van. In actual fact, with respect to the front of the vehicle, as the velocity of the fluid impinging on the front of the vehicle, especially the windshield increases, the pressure decreases. As the flow proceeds along the top of the vehicle, it moves relatively smoothly. However, the air particles in the boundary layer are unable to make the sharp change in direction and velocity required to negotiate the downward curve at the back of the van, especially in the presence of the adverse pressure gradient created by the low pressure along the roof.
The result is “flow separation.” The air behind the vehicle winds up moving faster than it ideally should. Bernoulli's equation tells us that the higher velocity will be accompanied by a lower pressure. This equation relates the pressure, velocity and height in the steady motion of an ideal fluid. The usual form is v2/2+p/ρ+gz=constant, where v is the velocity at a point, p the pressure, ρ the density, g the acceleration of gravity, and z the height above an arbitrary reference level. As a result, the pressure behind the van is much lower than atmospheric pressure and the air is “tumbling” in a pattern referred to as “eddies.”
It is mostly the low pressure behind the van which causes pressure drag. It acts similar to a vacuum sucking up the dust from the road, making the back of the vehicle, especially a bluff body van very dirty.
The above explanations are the fundamental reasons for most pressure drag on objects moving through the air; i.e., most pressure drag is due to low pressure behind the object, rather than high pressure ahead of the object.
It has been determined that when the air separating from the towing vehicle in the form of the eddy currents noted above, impinges on the front of a bluff body trailer, the parasite drag on the joined assembly increases substantially. When the air attempts to flow around the back of, e.g., a towing vehicle, the adverse pressure gradient soon causes the boundary layer to separate and the drag to increase dramatically.
The developed trailer of the present invention is in general a fairing which possesses a streamlined shape, especially the front or nose of same, so that the air is allowed to gradually decelerate along the back part of the trailer. This helps prevent the boundary layer from separating, and thus produces much less pressure drag.
The modern vehicles (automobiles and trucks) of today tend to possess a more streamline shape than their former counterparts, so when in motion, the vehicle, (in the case of the present invention, the towing car or truck) moves the oncoming air more smoothly out of the way, so there is less separation and formation of eddy currents at the rear of the vehicle the past. The instant combination of the streamlined automobile and the streamlined trailer result in less drag than combinations found in the prior art.
The side view of the profile of the front nose of the trailer of the instant invention follows a line having the general form of the equation y=1+log10X in the first and fourth quadrant of a unit circle. A top view of the lines forming the leading edge and sides of the trailer is that of a parabola. The three dimensional configuration having the streamlined shapes along the horizontal and vertical cross sectional axes results in a trailer possessing reduced drag when towed by a vehicle compared with the bluff bodied trailer found in the prior art. Experimental results show that the parasite drag which as noted is the sum of the pressure drag and the viscous drag in the vehicle-instant invention trailer combination is less than the parasite drag resulting from a towing vehicle-bluff body trailer.